Chemical Pesticides

Chemical pesticides (also known as plant protection products) are synthetically produced substances used in agriculture, forestry and horticulture to control, repel or kill harmful organisms. Their primary purpose is to secure crop yields and protect the quality of food from infestation.

Categorisation according to target organisms

Pesticides are usually classified according to their specific group of action:

Herbicides: Against unwanted weeds.
Insecticides: Against harmful insects.
Fungicides: Against fungal diseases.
Rodenticides: Against rodents.

Mode of action of chemical agents

The mechanisms of action are as diverse as the substances themselves. Chemical pesticides specifically interfere with the biological processes of the target organisms:

Nervous system (especially insecticides): Many agents act as neurotoxins. They block enzymes (e.g. acetylcholinesterase) or occupy receptors, leading to paralysis and death of the insect.
Metabolism & photosynthesis (herbicides): These inhibit vital processes in plants, such as energy production from light or the formation of amino acids.
Growth regulation: Certain active ingredients mimic hormones and thus disrupt the moulting of insects or the growth of plant cells.

Why are chemical agents a cause for concern?

Although pesticides contribute to global food security, they are controversial due to their environmental and health impacts:

Loss of biodiversity: Pesticides are often not selective enough. Insecticides also harm beneficial insects such as bees and butterflies. Herbicides destroy wild herbs, thereby depriving many animal species of their food source.
Residues in the food chain: Active substances enter the cycle via groundwater or direct application. Through bioaccumulation, they can accumulate in higher concentrations in predators or humans.
Health risks: Long-term exposure or high doses are suspected of being carcinogenic, disrupting the endocrine system or impairing fertility.
Resistance development: Harmful organisms develop defence mechanisms when exposed to frequent use, making it necessary to use newer and stronger active ingredients (the so-called "pesticide spiral").

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